Setting up an external fax in the FRITZ!Box

You can use a fax machine connected to an analog extension or the "FON S0" port of your FRITZ!Box to send and receive faxes over the Internet and/or your landline.

Important:Some of the settings described here are only displayed if the advanced view is enabled in the user interface. The configuration procedure and notes on functions given in this guide refer to the latest FRITZ!OS.

1 Enabling fax transmission with T.38

If you would like to use an Internet telephone number for faxing, then you must enable T.38 (fax over IP) for fax transmission in the FRITZ!Box. With T.38, a special network protocol is used for fax transmission instead of fax tones. As a result, transmission is significantly less susceptible to interference:

Click on "Change connection settings" in the "Telephony connection" section.

Enable the option "Fax transmission using T.38".

Click "Apply" to save the settings.

2 Enabling the fax switch (passive)

If you would like to use your analog landline number to receive telephone calls as well as faxes, enable the FRITZ!Box's fax switch. The fax switch recognizes whether an incoming call is a voice call or a fax call and automatically forwards faxes to a fax machine configured in the FRITZ!Box:

Important:A different device, for example a telephone or answering machine, must accept the call first in order for the fax switch to recognize faxes and forward them. The fax switch does not recognize calls that are not accepted.

3 Reconfiguring the fax machine

If the fax machine is already displayed in the list of telephony devices, click the button (delete) for the fax machine.

Reconfigure the fax machine: Click the "Configure New Device" button and follow the instructions.

If you cannot select the extension the fax device is connected to when configuring it, then another telephony device has already been configured for the extension. You must delete this device first.

If the fax machine is connected to the "FON S0" port on the FRITZ!Box, during the configuration procedure you will be shown which telephone numbers to assign to the fax machine. If the fax machine is connected by means of an ISDN PBX, you must assign the telephone numbers to the extension of the ISDN PBX with the fax machine.